void glGetProgramInfoLog(GLuint program, GLsizei maxLength, GLsizei *length, GLchar *infoLog)
glGetProgramInfoLog returns the information log for the specified program object. The information log for a program object is modified when the program object is linked or validated. The string that is returned is null terminated.
glGetProgramInfoLog returns in infoLog as much of the information log as it can, up to a maximum of maxLength characters. The number of characters actually returned, excluding the null termination character, is specified by length. If the length of the returned string is not required, a value of NULL can be passed in the length argument. The size of the buffer required to store the returned information log can be obtained by calling glGetProgram with the value GL_INFO_LOG_LENGTH.
The information log for a program object is either an empty string, a string containing information about the last link operation, or a string containing information about the last validation operation. It may contain diagnostic messages, warning messages, and other information. When a program object is created, its information log is a string of length 0.
glGetProgramInfoLog is available only if the GL version is 2.0 or greater.
The information log for a program object is the OpenGL implementor's primary mechanism for conveying information about linking and validating. Therefore, the information log can be helpful to application developers during the development process, even when these operations are successful. Application developers should not expect different OpenGL implementations to produce identical information logs.
GL_INVALID_VALUE is generated if program is not a value generated by OpenGL.
GL_INVALID_OPERATION is generated if program is not a program object.
GL_INVALID_VALUE is generated if maxLength is less than 0.
GL_INVALID_OPERATION is generated if glGetProgramInfoLog is executed between the execution of glBegin and the corresponding execution of glEnd.
glGetProgram with argument GL_INFO_LOG_LENGTH
glCompileShader, glGetShaderInfoLog, glLinkProgram, glValidateProgram